1/*
  2 * Cleancache frontend
  3 *
  4 * This code provides the generic "frontend" layer to call a matching
  5 * "backend" driver implementation of cleancache.  See
  6 * Documentation/vm/cleancache.txt for more information.
  7 *
  8 * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
  9 * Author: Dan Magenheimer
 10 *
 11 * This work is licensed under the terms of the GNU GPL, version 2.
 12 */
 13
 14#include <linux/module.h>
 15#include <linux/fs.h>
 16#include <linux/exportfs.h>
 17#include <linux/mm.h>
 18#include <linux/debugfs.h>
 19#include <linux/cleancache.h>
 20
 21/*
 22 * This global enablement flag may be read thousands of times per second
 23 * by cleancache_get/put/invalidate even on systems where cleancache_ops
 24 * is not claimed (e.g. cleancache is config'ed on but remains
 25 * disabled), so is preferred to the slower alternative: a function
 26 * call that checks a non-global.
 27 */
 28int cleancache_enabled __read_mostly;
 29EXPORT_SYMBOL(cleancache_enabled);
 30
 31/*
 32 * cleancache_ops is set by cleancache_ops_register to contain the pointers
 33 * to the cleancache "backend" implementation functions.
 34 */
 35static struct cleancache_ops cleancache_ops __read_mostly;
 36
 37/*
 38 * Counters available via /sys/kernel/debug/frontswap (if debugfs is
 39 * properly configured.  These are for information only so are not protected
 40 * against increment races.
 41 */
 42static u64 cleancache_succ_gets;
 43static u64 cleancache_failed_gets;
 44static u64 cleancache_puts;
 45static u64 cleancache_invalidates;
 46
 47/*
 48 * register operations for cleancache, returning previous thus allowing
 49 * detection of multiple backends and possible nesting
 50 */
 51struct cleancache_ops cleancache_register_ops(struct cleancache_ops *ops)
 52{
 53	struct cleancache_ops old = cleancache_ops;
 54
 55	cleancache_ops = *ops;
 56	cleancache_enabled = 1;
 57	return old;
 58}
 59EXPORT_SYMBOL(cleancache_register_ops);
 60
 61/* Called by a cleancache-enabled filesystem at time of mount */
 62void __cleancache_init_fs(struct super_block *sb)
 63{
 64	sb->cleancache_poolid = (*cleancache_ops.init_fs)(PAGE_SIZE);
 65}
 66EXPORT_SYMBOL(__cleancache_init_fs);
 67
 68/* Called by a cleancache-enabled clustered filesystem at time of mount */
 69void __cleancache_init_shared_fs(char *uuid, struct super_block *sb)
 70{
 71	sb->cleancache_poolid =
 72		(*cleancache_ops.init_shared_fs)(uuid, PAGE_SIZE);
 73}
 74EXPORT_SYMBOL(__cleancache_init_shared_fs);
 75
 76/*
 77 * If the filesystem uses exportable filehandles, use the filehandle as
 78 * the key, else use the inode number.
 79 */
 80static int cleancache_get_key(struct inode *inode,
 81			      struct cleancache_filekey *key)
 82{
 83	int (*fhfn)(struct inode *, __u32 *fh, int *, struct inode *);
 84	int len = 0, maxlen = CLEANCACHE_KEY_MAX;
 85	struct super_block *sb = inode->i_sb;
 86
 87	key->u.ino = inode->i_ino;
 88	if (sb->s_export_op != NULL) {
 89		fhfn = sb->s_export_op->encode_fh;
 90		if  (fhfn) {
 91			len = (*fhfn)(inode, &key->u.fh[0], &maxlen, NULL);
 92			if (len <= 0 || len == 255)
 93				return -1;
 94			if (maxlen > CLEANCACHE_KEY_MAX)
 95				return -1;
 96		}
 97	}
 98	return 0;
 99}
100
101/*
102 * "Get" data from cleancache associated with the poolid/inode/index
103 * that were specified when the data was put to cleanache and, if
104 * successful, use it to fill the specified page with data and return 0.
105 * The pageframe is unchanged and returns -1 if the get fails.
106 * Page must be locked by caller.
107 */
108int __cleancache_get_page(struct page *page)
109{
110	int ret = -1;
111	int pool_id;
112	struct cleancache_filekey key = { .u.key = { 0 } };
113
114	VM_BUG_ON(!PageLocked(page));
115	pool_id = page->mapping->host->i_sb->cleancache_poolid;
116	if (pool_id < 0)
117		goto out;
118
119	if (cleancache_get_key(page->mapping->host, &key) < 0)
120		goto out;
121
122	ret = (*cleancache_ops.get_page)(pool_id, key, page->index, page);
123	if (ret == 0)
124		cleancache_succ_gets++;
125	else
126		cleancache_failed_gets++;
127out:
128	return ret;
129}
130EXPORT_SYMBOL(__cleancache_get_page);
131
132/*
133 * "Put" data from a page to cleancache and associate it with the
134 * (previously-obtained per-filesystem) poolid and the page's,
135 * inode and page index.  Page must be locked.  Note that a put_page
136 * always "succeeds", though a subsequent get_page may succeed or fail.
137 */
138void __cleancache_put_page(struct page *page)
139{
140	int pool_id;
141	struct cleancache_filekey key = { .u.key = { 0 } };
142
143	VM_BUG_ON(!PageLocked(page));
144	pool_id = page->mapping->host->i_sb->cleancache_poolid;
145	if (pool_id >= 0 &&
146	      cleancache_get_key(page->mapping->host, &key) >= 0) {
147		(*cleancache_ops.put_page)(pool_id, key, page->index, page);
148		cleancache_puts++;
149	}
150}
151EXPORT_SYMBOL(__cleancache_put_page);
152
153/*
154 * Invalidate any data from cleancache associated with the poolid and the
155 * page's inode and page index so that a subsequent "get" will fail.
156 */
157void __cleancache_invalidate_page(struct address_space *mapping,
158					struct page *page)
159{
160	/* careful... page->mapping is NULL sometimes when this is called */
161	int pool_id = mapping->host->i_sb->cleancache_poolid;
162	struct cleancache_filekey key = { .u.key = { 0 } };
163
164	if (pool_id >= 0) {
165		VM_BUG_ON(!PageLocked(page));
166		if (cleancache_get_key(mapping->host, &key) >= 0) {
167			(*cleancache_ops.invalidate_page)(pool_id,
168							  key, page->index);
169			cleancache_invalidates++;
170		}
171	}
172}
173EXPORT_SYMBOL(__cleancache_invalidate_page);
174
175/*
176 * Invalidate all data from cleancache associated with the poolid and the
177 * mappings's inode so that all subsequent gets to this poolid/inode
178 * will fail.
179 */
180void __cleancache_invalidate_inode(struct address_space *mapping)
181{
182	int pool_id = mapping->host->i_sb->cleancache_poolid;
183	struct cleancache_filekey key = { .u.key = { 0 } };
184
185	if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
186		(*cleancache_ops.invalidate_inode)(pool_id, key);
187}
188EXPORT_SYMBOL(__cleancache_invalidate_inode);
189
190/*
191 * Called by any cleancache-enabled filesystem at time of unmount;
192 * note that pool_id is surrendered and may be reutrned by a subsequent
193 * cleancache_init_fs or cleancache_init_shared_fs
194 */
195void __cleancache_invalidate_fs(struct super_block *sb)
196{
197	if (sb->cleancache_poolid >= 0) {
198		int old_poolid = sb->cleancache_poolid;
199		sb->cleancache_poolid = -1;
200		(*cleancache_ops.invalidate_fs)(old_poolid);
201	}
202}
203EXPORT_SYMBOL(__cleancache_invalidate_fs);
204
205static int __init init_cleancache(void)
206{
207#ifdef CONFIG_DEBUG_FS
208	struct dentry *root = debugfs_create_dir("cleancache", NULL);
209	if (root == NULL)
210		return -ENXIO;
211	debugfs_create_u64("succ_gets", S_IRUGO, root, &cleancache_succ_gets);
212	debugfs_create_u64("failed_gets", S_IRUGO,
213				root, &cleancache_failed_gets);
214	debugfs_create_u64("puts", S_IRUGO, root, &cleancache_puts);
215	debugfs_create_u64("invalidates", S_IRUGO,
216				root, &cleancache_invalidates);
217#endif
218	return 0;
219}
220module_init(init_cleancache)